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J Extracted from Proceedings of The American Carnation Society, Eighth 
* Annual Meeting, Held in Philadelphia, February 16 and 17, 1899. 



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Sub-Watering 



AND 



DRY AIR IN GREENHOUSES. 



BY 3- 



J. C. ARTHUR. 
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A. T. De La Mare Printing and Publishing Co. Ltd., Rhinelander BuildiDg, New Torn. 



FEB 14 1905 
P. ofD, 




SUB-WATERING 



AND 



DRY AIR IN GREENHOUSES. 



The President • We will now be pleased to hear from 
Professor Arthur, who will read the paper he has prepared 
on Sub-watering and Dry Air in Greenhouses. 

Professor Arthur: I had no idea when I consented to 
give a paper on Sub-watering, that we would have such a 
demonstration of the disadvantages of excessive surface 
watering as we have to-night. Neither had I any idea 
that I should be called upon to expend so much energy in 
getting here, and it is doubtful whether I have a reason- 
able amount of energy left to present a paper. In my 
paper that I presented a year ago I made the attempt, not 
to present a new thing, but to present what had been 
fairly well demonstrated and reasonably well published, 
but which had not been taken up simply because it had 
not been brought to the attention of those who should be 
most interested in it — the practical men — in a way that 



57 



attracted their attention. So I attempted to do that 
one thing, and I am very much gratified indeed that the 
attempt should have succeeded so well that many have 
already made some effort in that direction, and some have 
made a very considerable attempt at demonstrating 
whether there is anything really good or not in the sug- 
gestion. The paper I have to present to-night is not very 
long, and it is in the way of a supplement to the first 
presentation. 

Sub-watering and Dry Air in Greenhouses* 

BY J. C. ARTHUR, OF THE PURDUE EXPERIMENT STATION. 

The time was when acceptable greenhouse culture 
called for a maximum growth without close inquiry into 
the question of healthy and normal development. The 
ideal of the gardener was a tropical jungle with steaming 
atmosphere, and a wealth of luscious foliage and flower. 

The use of glass houses for winter production of vege- 
tables and flowers delighting in cool weather, such as 
lettuce, radish, rose and carnation, brought with it some 
modification of the tropical ideal. But doubtless the most 
potent factor in changing the point of view has been the 
pressing necessity for protection against the many de- 
structive parasitic diseases. When the rust, smut, rot or 
mildew carried off a crop, as it did much oftener and 
more completely than in the open air, an inquiry into the 
causes of the epidemic revealed advantages in methods 
that eliminated the conditions that favored the growth of 
the fungus as fully as could be done without interfering 
with the growth of the crop. Incidentally it was learned 
that the old time notions reg-arding greenhouse methods 



58 



could be profitably modified, and a spirit of inquiry and 
willingness to change has been engendered, especially a 
desire to adapt the conditions to the fundamental needs of 
the crop grown, if such knowledge can be obtained. 

In citing the chief factors in changing the ideals in 
greenhouse culture one must not forget the subtle but 
potent influence of the long-stemmed flower. To meet the 
demands of fashion for a large flower upon a strong leafy 
stem of considerable length, very fortunately a demand 
that rests upon a healthy taste, although one that is some- 
times carried to extremes, the florist has been obliged to 
inquire into the conditions that especially promote a 
vigorous, yet substantial development. Besides produc- 
ing a large flower upon a long stem, thorough business 
success requires that the petals be of a lasting texture and 
the stem firm and substantial, and that each plant shall 
produce a maximum number of such blooms continuously 
for the season. Only high bred plants, strengthened 
along every hereditary channel, kept under conditions for 
well-balanced and healthy development, can meet these 
exacting requirements. 

A clear conception of the problem shows some radical 
defects in the old-time methods of rearing plants under 
glass. A year ago, in my paper before this Society 
under the caption, ''Moisture, the Plant's Greatest Re- 
quirement," I presented reasons for believing that for the 
flowers and vegetables usually grown in commercial 
greenhouses, wrong ideas prevailed regarding the dis- 
tribution and application of moisture. I pointed out that 
the plant would thrive best, especially the carnation, 
when the air was moderately dry, and the soil moist 
beneath and dry on the surface. To secure these condi- 



59 



tions I advocated the abandonment of surface spraying 
and watering, and the substitution of uniform watering 
from beneath the soil. 

My experience in presenting new methods to those who 
should presumably take the liveliest interest in them 
does not lead me to be sanguine of much support. I am 
often reminded of an attempt I once made to do a service 
to some elderly persons who had lived in a small town 
away from the direct lines of railway. Bananas were 
practically unknown in that region, and upon visiting 
them I carried some along at considerable inconvenience 
to myself. I expatiated upon the merits of the new 
fruit, but my friends would only take very small nibbles, 
and promptly came to the conclusion that they did not 
care for it, and said that I had better eat it myself, if I 
thought it was good. Some years afterward, when the 
town had grown and the shops were abundantly stocked 
with imported fruits, I paid a visit to the same old folks 
and found that bananas had become their special delight, 
and to live without them was a hardship. 

So I had thought that sub-watering, especially in large 
and progressive establishments, might come about in 
time, and naturally have been greatly surprised and grat- 
ified to learn that on the contrary it has been taken up 
with promptness, both by large and small growers, and 
not at all in a gingerly manner, but on a scale that is 
likely to demonstrate its good and weak points with rea- 
sonable clearness. 

The present paper is intended as a supplement to the 
former one, to strengthen some of the theoretical points 
and to amplify some of the practical details. In the first 
place I wish to call your attention to an able paper by Dr. 



60 



W. Wolley upon the influence of atmospheric moisture on 
the growth of plants, published a few months ago. The 
work was carried on at Munich in the experimental 
grounds of the Bavarian Agricultural College. Farm 
crops growing in the open field, including alfalfa, hairy 
vetch, barley, flax and potato, were used; and in order to 
control the amount of moisture in the air the experi- 
mental plants were covered with small houses, about 
three feet by six and five feet high, having glass on three 
sides. These houses were in groups of three, one having 
air like the outside air, one having it much moister and 
one much drier. The plants were enclosed and observa- 
tions taken throughout the whole growing season, the 
houses being large enough to permit normal develop- 
ment. The extra moist air was secured by allowing 
water to drip upon blotting paper, and the extra dry air 
by using an absorbant like chloride of calcium. The work 
was well carried out and the results can evidently be ac- 
cepted with confidence. 

The well established conclusions may be summed up in 
a few sentences, the details not being especially impor- 
tant in this connection. It is particularly interesting to 
learn that the ash content is always greater in plants 
grown in dry air, and even the dry weight is usually 
more, which being interpreted, means that in the dry air 
more water passes up through the plant, bearing with it 
more food material derived from the soil, and that this 
induces an increased production of solid matter in the 
plant. 

All parts of the plant become firmer in dry air, the 
woody fibers increase in strength, and the cuticle in thick- 
ness. This ensures a more substantial development, and 



61 



in most cases brings about a heavier harvest. It is ex- 
actly in line with the aims of the florist, who wishes cut 
flowers that will ship well and that will stand up well in 
heated rooms. 

A feature that is not so acceptable was the shortening 
of the stems and contraction of the leaves in the dry air, 
which was very marked in every trial. This is undoubt- 
edly due, as the author has indicated, to the loss of water 
from the foliage being so great in the dry air that the 
roots were unable to take it up fast enough from the soil 
to maintain the internal pressure, which necessarily pre- 
vented the cells from duly expanding. That the differ- 
ence in size of the organs was chiefly due to a deficiency 
of water supply is also evidenced by the failure of the po- 
tato tubers to properly increase and fill with starch in 
plants grown in dry air. Of course it remains an open 
question whether the roots would really take up sufficient 
water, if it were supplied to them abundantly to provide 
for the evaporation and still keep up the necessary inter- 
nal pressure for maximum growth. This is a question 
that can only be answered by actual experiment, which 
so far is lacking. 

From the Bavarian investigations we may safely infer 
that a moderately dry atmosphere promotes the substan- 
tial development of ordinary plants, increases the strength 
of stem and firmness of tissue, but that the full benefits 
can only be derived when there is an adequate supply of 
moisture for the roots. We may also believe from the 
knowledge we have derived from other sources, that 
plants in a dry atmosphere are less likely to take diseases. 

However, we are chiefly interested at present in the 
plant's demand' for water. What already has been said is 



62 



enough to indicate that the plant should have as much 
water supplied to it as can be taken up by the roots. I 
believe no argument is needed to convince my hearers 
that for greenhouse crops sub-watering is immensely 
superior to any system of surface watering. Since the 
presentation of my paper before this Society a year ago, 
many articles have been published commendatory of the 
method, and a number of practical and theoretical points 
elucidated that were not touched upon in my necessarily 
brief paper. 

From what has been published, and from my rather ex- 
tended correspondence, I am more fully than ever convinced 
that the use of tile for supplying water, and make-shifts 
in place of a thoroughly watertight bench bottom, which 
are generally selected on account of cheapness, are likely 
to bring disappointment. The most satisfactory lining, 
probably in the order named, is zinc, galvanized iron, or 
cement, which should extend three or four inches up the 
sides of the bench, or to the top, if the expense does not 
seem too great. The bottom is then covered with four 
inches of porous bricks, set so close together that soil will 
not drop between them ; and ample space is provided for 
water and air to circulate freely by removing about a half 
inch of the lower edges of the bricks before setting. The 
bed is then filled with soil in the usual manner. 

Water is run into the bottom of the bench through an 
inch tube set at intervals of five to ten feet along the 
front edge, or an even better way probably is the plan I 
recently saw in use in Mr. Fred. Dorner's houses, of using 
a flue about two by six inches instead of the tube. 
Mr. Dorner's plan permits water to run in a little easier 
from the hose, and does away with any necessity for 



63 



a gauge, as the bottom of the bench can be readily seen 
through the flues, and the presence or absence of standing 
water noted. 

Overflows should be provided at the back of the bench, 
so that only a certain depth of water can be added, even 
by the most careless workman. These can be placed at 
two inches above the bottom, which experience shows to 
be about right. 

These items cover the essential features of what is be- 
lieved to be at present the most perfect system of sub- 
watering. So far as the application in commercial houses 
has come to my knowledge, there seems to be misappre- 
hension of the full philosophy of the system. The soil 
should at all times be well supplied with air, which 
largely comes from beneath, and therefore should not be 
kept too wet. Unless benches are made far deeper than 
usual, water standing in the bottom of the bench any 
large part of the time cannot fail to keep the soil too wet, 
besides depriving it of the circulation of air that should 
take place through the brick. It must be remembered 
that the bricks continue to supply water to the soil above 
long after it has entirely disappeared from the bottom of 
the bench. The usual depth of soil is scarcely enough for 
this system, even with the most judicious attention. It 
would be better to have five or six inches of soil above 
the bricks, and then an inch of the surface soil can al- 
ways be kept dry to act as a mulch and protection against 
fungi. 

After a bench is first filled, water should be applied 
cautiously and time enough given for the slow process of 
diffusion. It will take from one to three days for the 
moisture to appear at the surface after water is run into 



64 



the bottom. Water enough for the operation can be sup- 
plied in two or three applications ; what more is added 
tends to puddle the soil and injure it. Patience is needed 
for the first watering, for it cannot be hurried, but can 
easily be overdone. 

In all subsequent watering it must be borne in mind 
that it takes a long time for the water that is put in the 
bottom to reach the upper layers of soil; and that no 
water is lost. At first when the plants are small, it will 
probably be sufficient to water once in one or two weeks. 
By a watering is meant to run water into the bench until 
it runs out at the overflow. In three or four hours it will 
all have been taken up by the bricks, and will be given up 
slowly to the soil. As the crop grows, watering must be 
more frequent, but will rarely need to be oftener than 
once in one to three days. If the surface of the bench 
does not keep dry, too much water is certainly being ap- 
plied. The amount to be used must be a matter of ex- 
perience, and requires careful judgment. The tendency 
at first is to over water. The process is so different from 
the usual surface method of watering that some time and 
close observation are required in order to fully master it, 
and obtain the greatest advantage from it. 

It will be a convenience in construction and give greater 
control over the watering, if the benches are divided into 
lengths of 25 or 30 feet by partitions. These sections can 
be at different levels, which will also provide for the slope 
in long houses. 

Experiments carried on since my last paper make it 
certain that the extra feeding of the plants can be done 
by applying the liquid fertilizer through the bottom, of 
course taking care that no solid material is allowed to pass 



65 

in to clog up the spaces beneath the bricks. This does 
away with all surface applications. 

If now the house be piped for water by running a line 
along the front of each bench, with an opening for each 
section of bench, the whole house can be watered at 
once with the opening and closing of a single stopcock. 
The saving of labor which this change implies must go 
some ways toward meeting the additional first cost of 
construction. 

Of course a house that is already piped in the 
ordinary way, with hose attachments provided, could not 
be changed profitably, but if a house is being built for 
this purpose, the hose can be entirely done away with, 
and a line of pipe run along the front of each bench, and 
the whole watering done by turning a single stop-cock, or 
stop-cocks can be added for each one of the different sec- 
tions, and then you have the house under more perfect 
control. 

There seems to be but little remaining that calls for the 
services of the Experiment Station. If it is found that 
the Stations have done a signal service to commercial 
horticulture, as it now appears, they ask nothing in re- 
turn but commendation, and a support that will increase 
their usefulness. 



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